Ask away as much as you like. That is what the forum is for - oh and for giving advice lol.
Okay, your nitrite is too high, should be at 0. Possibly you have some ammonia as well. Do you know what the nitrogen cycle is? Ammonia and nitrite will burn fins, tails and gills of fish, sometimes the damage is permanent and irreversible.
In a tank that size the male will be stressed and also will be stressing the females. You would be better with either a bigger tank with plenty of plants if you want to keep them together or keep them apart.
Can he stay in the tank he is now? If so add melafix to that tank, it is a 7 day dose cycle so keep dosing for 7 days and see if the tail repairs itself.